Ink is failing to form a continuous film
Adjust ink to reduce viscosity. Use a more active (wetter) solvent
Stock is too rough
Use electro-assist (with polar solvents)
There are imperfections in the stock
Adjust doctor blade to carry more ink. Use coating primer if possible
The ink is wrong for the substrate
Reformulate or replace ink
Film treatment is poor
Retreat or replace film
Worn cylinder, insufficient film transfer to cover substrate
Re-make cylinder